The Candidate is a pediatric rheumatologist with six years of clinical postdoctoral experience who has established a laboratory, secured funding and successfully developed a sensitive in vitro assay of cell-mediated immunity (CMI) particularly suitable for research involving children. The Research. The proposed work will examine the hypothesis that different patterns of autoimmunity to purified human antigens distinguish JRA patients with different patterns of disease. First, human collagen, proteoglycan or proteoglycan link protein will be purified from fetal skin or cartilage and characterized. Then mononuclear leukocytes (MNL) from JRA patients or control subjects will be incubated with the purified antigens. Cell-mediated immunity to the antigens will be measured using three assays: 1) the newly-developed enzyme induction assay, 2) an assay for leukocyte inhibitory factor (LIF), 3) a lymphocyte transformation (LT) assay. Histocompatibility typing also will be performed. Immune reactivity of JRA children and controls will be correlated with clinical and histocompatibility typing characteristics. Information from these studies may identify genetic and immunologic factors which interacts to determine, in part, the course of JRA. The Environment. The research will be conducted under supportive circumstances. Time will be guaranteed. The sponsor is an established investigator who will provide close supervision. Available to the candidate within and without the Department of Pediatrics is knowledgeable criticism and consultation for all aspects of this work.